What is the general solution for cos(x-45)=(-1)/2 ?

The general solution for cos(x-45)=(-1)/2 is x=360n+165,x=360n+285

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cos(x-45)=(-1)/2

Solution

cos (x - 4 5^{\circ}) = \frac{- 1}{2}

Solution

x = 36 0^{\circ} n + 16 5^{\circ}, x = 36 0^{\circ} n + 28 5^{\circ}

Radians

x = \frac{11 π}{12} + 2 πn, x = \frac{19 π}{12} + 2 πn

Solution steps

cos (x - 4 5^{\circ}) = \frac{- 1}{2}

Apply the fraction rule:

\frac{- a}{b} = - \frac{a}{b}

cos (x - 4 5^{\circ}) = - \frac{1}{2}

General solutions for

cos (x - 4 5^{\circ}) = - \frac{1}{2}

cos (x)

periodicity table with

36 0^{\circ} n

cycle:

x 0 3 0^{\circ} 4 5^{\circ} 6 0^{\circ} 9 0^{\circ} 12 0^{\circ} 13 5^{\circ} 15 0^{\circ} cos (x) 1 \frac{3}{2} \frac{2}{2} \frac{1}{2} 0 - \frac{1}{2} - \frac{2}{2} - \frac{3}{2} x 18 0^{\circ} 21 0^{\circ} 22 5^{\circ} 24 0^{\circ} 27 0^{\circ} 30 0^{\circ} 31 5^{\circ} 33 0^{\circ} cos (x) - 1 - \frac{3}{2} - \frac{2}{2} - \frac{1}{2} 0 \frac{1}{2} \frac{2}{2} \frac{3}{2}

x - 4 5^{\circ} = 12 0^{\circ} + 36 0^{\circ} n, x - 4 5^{\circ} = 24 0^{\circ} + 36 0^{\circ} n

x - 4 5^{\circ} = 12 0^{\circ} + 36 0^{\circ} n, x - 4 5^{\circ} = 24 0^{\circ} + 36 0^{\circ} n

Solve

x - 4 5^{\circ} = 12 0^{\circ} + 36 0^{\circ} n : x = 36 0^{\circ} n + 16 5^{\circ}

x - 4 5^{\circ} = 12 0^{\circ} + 36 0^{\circ} n

Move

4 5^{\circ}

to the right side

x - 4 5^{\circ} = 12 0^{\circ} + 36 0^{\circ} n

Add

4 5^{\circ}

to both sides

x - 4 5^{\circ} + 4 5^{\circ} = 12 0^{\circ} + 36 0^{\circ} n + 4 5^{\circ}

Simplify

x - 4 5^{\circ} + 4 5^{\circ} = 12 0^{\circ} + 36 0^{\circ} n + 4 5^{\circ}

Simplify

x - 4 5^{\circ} + 4 5^{\circ} : x

x - 4 5^{\circ} + 4 5^{\circ}

Add similar elements:

- 4 5^{\circ} + 4 5^{\circ} = 0

= x

Simplify

12 0^{\circ} + 36 0^{\circ} n + 4 5^{\circ} : 36 0^{\circ} n + 16 5^{\circ}

12 0^{\circ} + 36 0^{\circ} n + 4 5^{\circ}

Group like terms

= 36 0^{\circ} n + 4 5^{\circ} + 12 0^{\circ}

Least Common Multiplier of

4, 3 : 12

4, 3

Least Common Multiplier (LCM)

Prime factorization of

4 : 2 \cdot 2

4

4

divides by

24 = 2 \cdot 2

= 2 \cdot 2

Prime factorization of

3 : 3

3

3

is a prime number, therefore no factorization is possible

= 3

Multiply each factor the greatest number of times it occurs in either

4

3

= 2 \cdot 2 \cdot 3

Multiply the numbers:

2 \cdot 2 \cdot 3 = 12

= 12

Adjust Fractions based on the LCM

Multiply each numerator by the same amount needed to multiply its

corresponding denominator to turn it into the LCM

12

For

4 5^{\circ} :

multiply the denominator and numerator by

3

4 5^{\circ} = \frac{18 0 ^{\circ} 3}{4 \cdot 3} = 4 5^{\circ}

For

12 0^{\circ} :

multiply the denominator and numerator by

4

12 0^{\circ} = \frac{36 0 ^{\circ} 4}{3 \cdot 4} = 12 0^{\circ}

= 4 5^{\circ} + 12 0^{\circ}

Since the denominators are equal, combine the fractions:

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{18 0 ^{\circ} 3 + 144 0 ^{\circ}}{12}

Add similar elements:

54 0^{\circ} + 144 0^{\circ} = 198 0^{\circ}

= 36 0^{\circ} n + 16 5^{\circ}

x = 36 0^{\circ} n + 16 5^{\circ}

x = 36 0^{\circ} n + 16 5^{\circ}

x = 36 0^{\circ} n + 16 5^{\circ}

Solve

x - 4 5^{\circ} = 24 0^{\circ} + 36 0^{\circ} n : x = 36 0^{\circ} n + 28 5^{\circ}

x - 4 5^{\circ} = 24 0^{\circ} + 36 0^{\circ} n

Move

4 5^{\circ}

to the right side

x - 4 5^{\circ} = 24 0^{\circ} + 36 0^{\circ} n

Add

4 5^{\circ}

to both sides

x - 4 5^{\circ} + 4 5^{\circ} = 24 0^{\circ} + 36 0^{\circ} n + 4 5^{\circ}

Simplify

x - 4 5^{\circ} + 4 5^{\circ} = 24 0^{\circ} + 36 0^{\circ} n + 4 5^{\circ}

Simplify

x - 4 5^{\circ} + 4 5^{\circ} : x

x - 4 5^{\circ} + 4 5^{\circ}

Add similar elements:

- 4 5^{\circ} + 4 5^{\circ} = 0

= x

Simplify

24 0^{\circ} + 36 0^{\circ} n + 4 5^{\circ} : 36 0^{\circ} n + 28 5^{\circ}

24 0^{\circ} + 36 0^{\circ} n + 4 5^{\circ}

Group like terms

= 36 0^{\circ} n + 4 5^{\circ} + 24 0^{\circ}

Least Common Multiplier of

4, 3 : 12

4, 3

Least Common Multiplier (LCM)

Prime factorization of

4 : 2 \cdot 2

4

4

divides by

24 = 2 \cdot 2

= 2 \cdot 2

Prime factorization of

3 : 3

3

3

is a prime number, therefore no factorization is possible

= 3

Multiply each factor the greatest number of times it occurs in either

4

3

= 2 \cdot 2 \cdot 3

Multiply the numbers:

2 \cdot 2 \cdot 3 = 12

= 12

Adjust Fractions based on the LCM

Multiply each numerator by the same amount needed to multiply its

corresponding denominator to turn it into the LCM

12

For

4 5^{\circ} :

multiply the denominator and numerator by

3

4 5^{\circ} = \frac{18 0 ^{\circ} 3}{4 \cdot 3} = 4 5^{\circ}

For

24 0^{\circ} :

multiply the denominator and numerator by

4

24 0^{\circ} = \frac{72 0 ^{\circ} 4}{3 \cdot 4} = 24 0^{\circ}

= 4 5^{\circ} + 24 0^{\circ}

Since the denominators are equal, combine the fractions:

\frac{a}{c} \pm \frac{b}{c} = \frac{a \pm b}{c}

= \frac{18 0 ^{\circ} 3 + 288 0 ^{\circ}}{12}

Add similar elements:

54 0^{\circ} + 288 0^{\circ} = 342 0^{\circ}

= 36 0^{\circ} n + 28 5^{\circ}

x = 36 0^{\circ} n + 28 5^{\circ}

x = 36 0^{\circ} n + 28 5^{\circ}

x = 36 0^{\circ} n + 28 5^{\circ}

x = 36 0^{\circ} n + 16 5^{\circ}, x = 36 0^{\circ} n + 28 5^{\circ}

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Frequently Asked Questions (FAQ)

What is the general solution for cos(x-45)=(-1)/2 ?
The general solution for cos(x-45)=(-1)/2 is x=360n+165,x=360n+285